I have a pretty bad bone bruise from the bar crashing on my sternoclavicular joint. Everytime I Clean it reaggravates. even with the techniques used in Greg's book. Yes, sometimes I don't get the technique perfect and it crashes.

How common is this and once it is injured how do you prevent reaggravating it. I did a period of no cleans for 3 months.

I've been having this same problem. I'm yet to find a way around it, I just kind of work through the discomfort of having the bar hit there. I refuse to go a full three months without doing a clean, I've just decided to basically go back to square one and MASTER the movement with lighter weights and VERY high speed. If you do find a solution to this let me know as I've been looking for one for a while now!